Feature Of The Week 1/17/10: Full-Field Optical Coherence Tomography for the Rapid Estimation of Epidermal Thickness
Feature Of The Week 1/17/10: A number of recent developments in non-invasive physiological monitoring of the human body have demonstrated a high potential for the use of such techniques in the in vivo estimation of various clinically relevant parameters such as haemoglobin content and its’ oxygen saturation, amount of glycated haemoglobin, alcohol, etc. One of the most promising of those parameters is the non-invasive estimation of tissue glucose concentration which can potentially bring a great relief for the patients with Diabetes Mellitus, for whom the tight glucose control is the major requirement for long term therapy.
The majority of the non-invasive methods perform the measurements through the skin. This is the outermost organ of the human body which demonstrates significant variations in its properties among different body sites and population. It is thus expected that the morphological structure of the skin at the measurement site might have an effect on the performance of such devices. In order to evaluate such influences, a rapid and reliable method for the characterisation of the relevant skin parameters is necessary.
A full-field optical coherence tomography (OCT) microscope (Heliotis AG) with parallel detection technology has been applied for the determination of the skin epidermal thickness in a study performed by Solianis Monitoring AG (Zürich, Switzerland). The OCT scans have been collected without direct skin contact and preliminary chemical treatment of the imaged area followed by a fully automatic analysis with an original algorithm. The OCT estimates were compared with the epidermal thickness derived by an experienced dermatologist from the optical histology of the neighbouring skin site performed with the Laser Scanning Confocal Microscope. The dorsal skin of the upper arm of 22 patients with Type 1 Diabetes Mellitus was investigated during the clinical study in the University Hosptial in Zürich.
The results indicate that the OCT parameter which has the highest correlation (R^2=0.657 and p<10^-4 ) with the epidermal thickness is the distance from the entrance signal to the first minimum of the reflectance. Thus the epidermal thickness characterisation can be performed rapidly (a few minutes including preparation) and reliably using the parallel OCT system.